Scott Watson supporters protest murder convictions

Supporters of double murderer Scott Watson have held a number of vigils today, protesting against the 45-year-old's convictions for murder.

Watson has been in prison for more than 18 years, but these people are still determined he's innocent.

The groups gathered in Blenheim and Christchurch, and tried to encourage others to help clear Watson's name.

"Easy to see that he's innocent - just a quick read through the actual evidence, you come to the conclusion pretty fast it wasn't him. There's no way he could've done it," says organiser Miranda Clare.

Watson was convicted for the 1999 murders of Ben Smart and Olivia Hope. Appeals against the convictions were rejected by the Privy Council and the Governor-General.

However, his father is still fighting for his freedom.

"There was never any hard evidence, at all. Any that they did have or looked like they did have, has evaporated in the years since," says his father, Chris Watson.

Watson even has the support of one of New Zealand's most wronged men, Arthur Allan Thomas, who was granted a Royal pardon and compensation.

"The system can get it wrong, in my day - that's why I'm here," says Mr Thomas.

"In my days, two juries found me guilty, and I'm totally innocent of the crime. The system can get it wrong."

Not everyone agreed with today's protesters.

"I'm not representing the police or anyone else; I'm representing myself, and you guys are all f***wits and losers," said one angry man.

A psychologist told the last Parole Board meeting that Watson remained "a high risk of being a menace to society".

He's up for parole again in December.

"Yeah it's really upsetting how long Scott has spent in prison for something he can't be charged beyond reasonable doubt, because the whole case is stacked full of doubt," say protest organisers.

His father is convinced social justice groups like this will help overturn his son's conviction.